Semiconductor device and method of manufacturing the same

ABSTRACT

In the present invention, the bonding pad is formed in a lattice-like shape. Directly underneath the passivation layer, the etching stopper layer is provided. An opening is made through the passivation layer and the etching stopper layer so as to expose the bonding pad. The cavity sections of the lattice-like shape of the bonding pad are filled with the insulating layer. The bonding wire is connected to the lattice-shaped bonding pad. With this structure, the bonding error of the device manufactured by the damascening process can be avoided.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a semiconductor device having amulti-layer wiring structure made by a damascening process or a dualdamascening process, and a method of manufacturing such a device.

[0002] An ultra-large scale integrated circuit (ULSI) employs amultilayer wiring structure in which wiring layers of three levels ormore are formed.

[0003]FIGS. 1 and 2 show a semiconductor device prepared by aconventional wiring process. FIG. 2 is a cross sectional view takenalong the line II-II indicated in FIG. 1.

[0004] As can be seen in the figure, a field oxide layer 12 is formed ona semiconductor substrate 11. In an element region surrounded by thefield oxide layer 12, a MOS transistor having a source-drain region 13and a gate electrode 14, is formed.

[0005] On the semiconductor substrate 11, an insulating layer 15 isformed so as to completely cover the MOS transistor. A contact hole 16is made in the insulating layer 15 from its surface to be through to thesource-drain region 13. On the insulating layer 15, a first-level wiringlayer having a plurality of wiring layers 17 is formed. Each of theplurality of wiring layers 17 is connected to the source-drain region 13of the MOS transistor via the contact hole 16.

[0006] On the insulating layer 15, an insulating layer (interlayerdielectric) 18 is formed so as to completely cover the plurality ofwiring layers 17. A contact hole 19 is made in the insulating layer 18from its surface to be through to the plurality of wirings 17. On theinsulating layer (interlayer dielectric) 18, a second-level wiring layerhaving a plurality of wiring layers 20 is formed. Each of the pluralityof wiring layers 20 is connected to the wiring layers 17 of thefirst-level wiring layers via the contact hole 19.

[0007] On the insulating layer (interlayer dielectric) 18, a bonding pad21 is formed. Further, on the insulating layer (interlayer dielectric)18, an insulating layer (passivation dielectric) 22 is formed so as tocompletely cover the plurality of wiring layers 20 and the bonding pad21. An opening 23 is made in the insulating film (passivationdielectric) 22 so as to expose the bonding pad 21.

[0008] In a semiconductor device manufactured by the conventional wiringprocess., a plurality of wirings 17 of the first-level wiring layer, aplurality of wirings 20 of the second-level wiring layer and the bondingpad 21 are formed by a photo engraving process (PEP), in which, a resistpattern is formed, and using the resist pattern as a mask, metal layersare etched by an anisotropic etching (such as RIE).

[0009] However, in an ULSI, the distance between wirings of the samelevel is becoming very narrow.

[0010] Therefore, the following drawbacks begin to arise.

[0011] First, it is very difficult to accurately pattern the wirings 17and 20 of the wiring layers. This is because the resolution of theexposing device for forming resist patterns, cannot follow up wiringpatterns which are becoming finer as the technology develops.

[0012] Second, it is very difficult to fill grooves resulting betweenwirings of the same level, with insulating layer, and therefore cavitiesare inevitably created between the wirings. This is because of a poorstep coverage of the insulating layer. Such cavities adversely affectthe multilayer wiring technique.

[0013]FIGS. 3 and 4 show a semiconductor device manufactured by a dualdamascening process. FIG. 4 is a cross sectional view taken along theline IV-IV indicated in FIG. 3.

[0014] As can be seen in the figure, a field oxide layer 12 is formed ona semiconductor substrate 11. In an element region surrounded by thefield oxide layer 12, a MOS transistor having a source-drain region 13and a gate electrode 14, is formed.

[0015] On the semiconductor substrate 11, insulating layers 15 and 24are formed so as to completely cover the MOS transistor. A contact hole16 is made in the insulating layers 15 and 24 from its surface to bethrough to the source-drain region 13.

[0016] The insulating layer 25 is formed on the insulating layer 24. Inthe insulating layer 25, a plurality of grooves 16 b used for forming afirst-level wiring layer, is formed. Bottom sections of the plurality ofgrooves 16 b are made through to the contact hole 16 a.

[0017] A barrier metal 17 a is formed on an inner surface of each of thecontact hole 16 a and the grooves 16. Further, on each of the barriermetals 17 a, a metal (or metal alloy) portion 17 b is formed so as tocompletely fill each of the contact hole 16 a and the grooves 16 b. Theplurality of wirings which make the first level wiring layer, consist ofthe barrier metals 17 a and the metal portions 17 b.

[0018] The surface of the insulating layer 25 meets with that of thefirst-level wiring layer, and the surface is made flat. Each of theplurality of wirings which give rise to the first-level wiring layer, isconnected to the source-drain region 13 of the MOS transistor.

[0019] On the insulating layer 25 and the first level wiring layer, theinsulating layer (interlayer dielectric) 18 and the insulating layer 26are formed. A contact hole 19 a is formed in the insulating layers 18and 26 from its surface to be through to the first-level wiring layer.

[0020] An insulating layer 27 is formed on the insulating film 26. Aplurality of grooves 19 b used for forming the second-level wiringlayer, are formed in the insulating layer 27. Bottom sections of theplurality of grooves 19 b are made through to the contact hole 19 a.

[0021] A barrier metal 20 a is formed on an inner surface of each of thecontact hole 19 a and the grooves 19 b. Further, on each of the barriermetals 20 a, a metal (or metal alloy) portion 20 b is formed so as tocompletely fill each of the contact hole 19 a and the grooves 19 b. Theplurality of wirings which make the second level wiring layer, consistof the barrier metals 20 a and the metal portions 20 b.

[0022] The surface of the insulating layer 27 meets with that of thesecond-level wiring layer, and the surface is made flat. Each of theplurality of wirings which give rise to the second-level wiring layer,is connected to the first-level wiring layer.

[0023] In the case where the second-level wiring layer is located as theuppermost layer, a part of the second-level wiring layer constitutes abonding pad 21. The bonding pad 21 is made of a metal (or metal alloy),as in the case of the second-level wiring layer.

[0024] An insulating layer (passivation dielectric) 22 is formed on theinsulation layer 27, the second-level wiring layer and the bonding pad21. An opening 23 is made in the insulating layer 22 so as to expose thebonding pad 21.

[0025] Regarding the semiconductor device manufactured by the dualdamascening process as described above, it is able to solve thedrawbacks of the conventional wiring process, that is, the wiringpattern becoming out of focus when exposing, and the cavities resultingbetween wirings.

[0026] However, in the dual damascening process or damascening process,the chemical mechanical polishing (CMP) technique is employed. In thecase where a bonding pad 21 is formed by the CMP technique, the centralportion of the bonding pad 21 is excessively etched, resulting indishing, that is, the bonding pad 21 is made into a dish-like shape.

[0027]FIG. 5 illustrates how dishing occurs.

[0028] More specifically, the CMP not only mechanically etch the metallayer 21′, but also chemically etch it. Therefore, in the case where themetal layer 21 (bonding pad) remains in a groove 19 b which has a widthsufficiently large as compared to its depth (note that the size of abonding pad is usually about 100 μm×100 μm), the central portion of themetal layer 21 in the groove 19 b is excessively etched mainly bychemical etching.

[0029] Such dishing easily causes a bonding error, that is, a wirecannot be bonded to the bonding pad 21 accurately during a wiringbonding operation, which results in the deterioration of the productionyield.

[0030]FIGS. 6 and 7 show a semiconductor device formed by the dualdamascening process, which has been proposed to solve the problem ofdishing. FIG. 7 is a cross sectional view taken along the line VII-VIIindicated in FIG. 6.

[0031] As can be seen in the figure, a field oxide layer 12 is formed ona semiconductor substrate 11. In an element region surrounded by thefield oxide layer 12, a MOS transistor having a source-drain region 13and a gate electrode 14, is formed.

[0032] On the semiconductor substrate 11, insulating layers 15 and 24are formed so as to completely cover the MOS transistor. A contact hole16 is made in the insulating layers 15 and 24 from its surface to bethrough to the source-drain region 13.

[0033] The insulating layer 25 is formed on the insulating layer 24. Inthe insulating layer 25, a plurality of grooves 16 b used for forming afirst-level wiring layer, are formed. Bottom sections of the pluralityof grooves 16 b are made through to the contact hole 16 a.

[0034] A barrier metal 17 a is formed on an inner surface of each of thecontact hole 16 a and the grooves 16. Further, on each of the barriermetals 17 a, a metal (or metal alloy) portion 17 b is formed so as tocompletely fill each of the contact hole 16 a and the grooves 16 b. Theplurality of wirings which make the first level wiring layer, consist ofthe barrier metals 17 a and the metal portions 17 b.

[0035] The surface of the insulating layer 25 meets with that of thefirst-level wiring layer, and the surface is made flat. Each of theplurality of wirings which give rise to the first-level wiring layer, isconnected to the source-drain region 13 of the MOS transistor.

[0036] On the insulating layer 25 and the first level wiring layer, theinsulating layer (interlayer dielectric) 18 and the insulating layer 26are formed. A contact hole 19 a is formed in the insulating layers 18and 26 from its surface to be through to the first-level wiring layer.

[0037] An insulating layer 27 is formed on the insulating film 26. Aplurality of grooves 19 b used for forming the second-level wiringlayer, are formed in the insulating layer 27. Bottom sections of theplurality of grooves 19 b are made through to the contact hole 19 a.

[0038] A barrier metal 20 a is formed on an inner surface of each of thecontact hole 19 a and the grooves 19 b. Further, on each of the barriermetals 20 a, a metal (or metal alloy) portion 20 b is formed so as tocompletely fill each of the contact hole 19 a and the grooves 19 b. Theplurality of wirings which make the second level wiring layer, consistof the barrier metals 20 a and the metal portions 20 b.

[0039] The surface of the insulating layer 27 meets with that of thesecond-level wiring layer, and the surface is made flat. Each of theplurality of wirings which give rise to the second-level wiring layer,is connected to the first-level wiring layer.

[0040] In the case where the second-level wiring layer is located as theuppermost layer, a part of the second-level wiring layer constitutes abonding pad 21. The bonding pad 21 is made of a metal (or metal alloy),as in the case of the second-level wiring layer.

[0041] However, in order to prevent the dishing which may occur duringthe CMP, the bonding pad 21 is formed to have a lattice-like shape. Morespecifically, in the bonding pad 21, a plurality of dot-like holes whichare arranged in a matrix manner are made.

[0042] An insulating layer (passivation dielectric) 22 is formed on theinsulation layer 27 and the second-level wiring layer. An opening 23 ismade in the insulating layer 22 so as to expose the bonding pad 21.

[0043] In the semiconductor device manufactured by the dual damasceningprocess, the bonding pad 21 is formed to have a lattice-like shape.Therefore, even in the case where the bonding pad 21 is formed by use ofthe CMP technique, the necessary portion is not excessively etched,thereby effectively preventing the dishing.

[0044] Next, the method of manufacturing a semiconductor device shown inFIGS. 6 and 7 will be described.

[0045] First, as can be seen in FIG. 8, with the LOCOS method, a fieldoxide layer 12 is formed on a silicon substrate 11. After that, in anelement region surrounded by the field oxide layer 12, a MOS transistorhaving a source-drain region 13 and a gate electrode 14 is formed.

[0046] Further, as an alternative, an insulating film (borophosphosilicate glass (BPSG) or the like) 15 having a thickness of about 1 μm,which completely covers the MOS transistor, is formed on the siliconsubstrate 11. The surface of the insulating layer 15 is made flat by theCMP.

[0047] Next, as can be seen in FIG. 9, an etching stopper layer 24 andan insulating layer 25 are formed continuously on the insulating film 15with the CVD method, for example. The insulating layer 25 is made of,for example, silicon oxide. In the case where the insulating layer 25 ismade of silicon oxide, the etching stopper layer 24 is made of amaterial having a high etching selectivity against silicon oxide inreactive ion etching (RIE), that is, for example, silicon nitride.

[0048] The thickness of the etching stopper layer 24 is set to about 50nm, and the thickness of the insulating film 25 is set to the same asthat of the wirings which constitute the first-level wiring layer, thatis, for example, about 0.6 μm.

[0049] Next, as can be seen in FIG. 10, a plurality of grooves 16 b areformed in the insulating layer 25. The plurality of grooves 16 b areformed by a photo engraving process, more specifically, the applicationof a resist on the insulating layer 25, the patterning of the resist,the etching of the insulating layer 25 by RIE using the resist as amask, and the removal of the resist. The etching stopper layer 24 servesas an etching stopper for the RIE.

[0050] It should be noted that the pattern of the plurality of grooves16 b is made to match with the pattern of the wirings which constitutethe first-level wiring layer.

[0051] Next, as can be seen in FIG. 11, a contact hole 16 a is made inthe insulating layers 15 and 24. The contact hole 16 a is made also bythe photo engraving process as in the formation of the plurality ofgrooves 16 b. More specifically, the contact hole 16 a is made byapplying a resist on the insulating layer 25 and in the grooves 16 b,patterning the resist, etching the insulating layers 15 and 24 by theRIE using the resist as a mask, and removing the resist.

[0052] Then, as can be seen in FIG. 12, a barrier metal 17 a is formedon the insulating layer 25, on an inner surface of the contact hole 16 aand the inner surfaces of the grooves 16 b, by the CVD method or PVDmethod. The barrier metal 17 a is made of, for example, a lamination oftitanium and titanium nitride, or silicon titanium nitride, or the like.

[0053] Next, as can be seen in FIG. 13, a metal (or metal alloy) portion17′ which completely covers the contact hole 16 a and the grooves 16 b,is formed on the barrier metal 17 a by the CVD or PVD method. The metalportion 17′ is made of, for example, aluminum, copper or an alloy ofthese metals.

[0054] As the PVD method which is used to form the metal portion 17′,the high temperature PVD method or a PVD method including such atemperature process that can completely fill the contact holes 16 a andthe grooves 16 b, is used.

[0055] Next, as can be seen in FIG. 14, the sections of the barriermetal 17 a and the metal portion 17 b, which are situated outside thecontact holes 16 a and the grooves 16 b, are etched by the CMP method,so that the barrier metal 17 a and the metal portion 17 b remain only inthe contact holes 16 a and the grooves 16 b.

[0056] In this manner, the first-level wiring layer is formed, and atthe same time, a contact plug which serves to electrically connect thefirst-level wiring layer and the diffusion layer (source-drain region)of the substrate to each other, is formed.

[0057] Next, as can be seen in FIG. 15, an insulating layer (forexample, silicon oxide) 18 having a thickness of about 1 μm, is formedon the insulating layer 25 and the first-level wiring layer by the CVDmethod. Further, an etching stopper layer 26 and an insulating layer 27are formed to be continuous on the insulating film 18 with the CVDmethod, for example. The insulating layer 27 is made of, for example,silicon oxide. In the case where the insulating layer 27 is made ofsilicon oxide, the etching stopper layer 26 is made of a material havinga high etching selectivity against silicon oxide in reactive ion etching(RIE), that is, for example, silicon nitride.

[0058] The thickness of the etching stopper layer 26 is set to about 50nm, and the thickness of the insulating film 27 is set to the same asthat of the wirings which constitute the second-level wiring layer, thatis, for example, about 0.6 μm.

[0059] Next, as can be seen in FIGS. 16 and 17, a plurality of grooves19 b and 19 b′ are formed in the insulating layer 25. The plurality ofgrooves 19 b and 19 b′ are formed by a photo engraving process, morespecifically, the application of a resist on the insulating layer 27,the patterning of the resist, the etching of the insulating layer 27 byRIE using the resist as a mask, and the removal of the resist. Theetching stopper layer 26 serves as an etching stopper for the RIE.

[0060] It should be noted that the pattern of the plurality of grooves19 b and 19 b′ is made to match with the pattern of the wirings whichconstitute the second-level wiring layer. The pattern of the grooves 19b′ is the same as that of the bonding pad (lattice-like shape) (in thecase where the second-level wiring layer is the uppermost layer).

[0061] Further, a contact hole 19 a is made in the insulating layers 18and 26. The contact hole 19 a is made also by the photo engravingprocess as in the formation of the plurality of grooves 19 b and 19 b′.More specifically, the contact hole 19 a is made by applying a resist onthe insulating layer 27 and in the grooves 19 b and 19 b′, patterningthe resist, etching the insulating layers 18 and 26 by the RIE using theresist as a mask, and removing the resist.

[0062] After that, as can be seen in FIGS. 18 and 19, a barrier metal 20a is formed on the insulating layer 27, on an inner surface of thecontact hole 19 a and the inner surfaces of the grooves 19 b and 19 b′,by the CVD method or PVD method. The barrier metal 20 a is made of, forexample, a lamination of titanium and titanium nitride, or silicontitanium nitride, or the like.

[0063] Further, metal (or metal alloy) portions 20 b and 21 whichcompletely cover the contact hole 19 a and the grooves 19 b and 19 b′,are formed on the barrier metal 20 a by the CVD or PVD method. The metalportions 20 b and 21 are made of, for example, aluminum, copper or analloy of these metals.

[0064] As the PVD method which is used to form the metal portions 20 band 21, the high temperature PVD method or a PVD method including such atemperature process that can completely fill the contact hole 19 a andthe grooves 19 b and 19 b′, is used.

[0065] After that, the sections of the barrier metal 20 a and the metalportions 20 b and 21, which are situated outside the contact hole 19 aand the grooves 19 b and 19 b′, are etched by the CMP method, so thatthe barrier metal 20 a and the metal portions 20 b and 21 remain only inthe contact hole 19 a and the grooves 19 b and 19 b′.

[0066] In this manner, the second-level wiring layer and the bonding padhaving a lattice-like shape are formed, and at the same time, a contactplug which serves to electrically connect the first-level wiring layerand the second-level wiring layer to each other, is formed.

[0067] Next, as can be seen in FIG. 20, a passivation layer 22 is formedon the insulating layer 27, the second-level wiring layer and thebonding pad, by, for example, the CVD method. The passivation layer 22is made of, for example, silicon oxide.

[0068] Next, as can be seen in FIGS. 21 and 22, an opening 23 is formedin the passivation layer 22. The opening 23 is situated so as to thelattice-shaped bonding pad 21, and is formed by a photo engravingprocess, more specifically, the application of a resist on theinsulating layer 22, the patterning of the resist, the etching of theinsulating layer 22 by RIE using the resist as a mask, and the removalof the resist.

[0069] In the RIE operation for making the opening 23, usually theinsulating layer 27 is etched as well since the insulating layers 22 and27 are made of the same material (for example, silicon oxide).

[0070] The feature of the semiconductor device manufactured by theabove-described dual damascening process or damascening process is thatthe metal portion itself which gives rise to wirings is not patterned,but the insulating layer is patterned. Since there is no process forfilling the sections between wirings with the insulating layer, nocavities are formed between wirings.

[0071] Further, in some cases, copper, which has a low resistance, isused to form wirings; however it is known to be very difficult toperform a patterning on copper. In the dual damascening process ordamascening process, the patterning of copper is not carried out, butthe wirings are formed by filling grooves of an insulating layer withcopper. Thus, the wirings made of copper are realized.

[0072] Further, in the dual damascening process, wirings and contactplugs can be formed at the same time, and therefore the production costcan be reduced.

[0073] However, in the dual damascening process, the RIE operated tomake the opening 23 to expose the bonding pad 21, inevitably serves toetch the insulating layer 27 at the same time. This is because theinsulating layers 22 and 27 are made of the same material (for example,silicon oxide) as described above.

[0074] In the above-described case, as shown in FIGS. 23 and 24, a wirebonding operation can easily result in that a wire 28 squash thelattice-shaped bonding pad 21, which may cause a bonding error. This isbecause portions of the lattice-like bonding pad 21 are cavities, whichmay easily cause the deformation of the bonding pad 21.

BRIEF SUMMARY OF THE INVENTION

[0075] The present invention has been proposed as a solution to theabove-described drawback of the conventional technique, and the objectthereof is as follows. That is, regarding the semiconductor devicemanufactured by the dual damascening process or damascening process, thebonding pad is formed to have a lattice shape, and the deformation ofthe lattice-shaped bonding pad is prevented so as to suppress bondingerror, thereby improving the reliability and yield of the product.

[0076] In order to achieve the above-described object, there isprovided, according to the present invention, a semiconductor deviceincluding: a bonding pad constituted by a conductive member filled ingrooves made in an insulating layer having a flat surface; an etchingstopper layer formed on the insulating layer and having an opening toexpose the bonding pad; and a passivation layer formed on the etchingstopper layer and having an opening to expose the bonding pad.

[0077] The grooves of the insulating layer are arranged in alattice-like shape and the bonding pad has a lattice-like shape. Theinsulating layer and the passivation layer are made of silicon oxide,and the etching stopper layer is made of silicon nitride.

[0078] Further, according to the present invention, there is provided amethod of manufacturing a semiconductor device, in which a bonding padis formed by making grooves in an insulating layer having a flat surfaceand filling the grooves with a conductive material, the method includingthe stops of: forming an etching stopper layer on the insulating layerand the bonding pad, the etching stopper layer being made of a materialwhich can be etched selectively with respect to at least a materialwhich is used to form the insulating layer; forming a passivation layeron the etching stopper layer, the passivation layer being made of amaterial which can be etched selectively with respect to at least thematerial used to form the etching stopper layer; removing only a portionof the passivation layer, which is situated above the bonding pad; andremoving only a portion of the etching stopper layer, which is situatedabove the bonding pad.

[0079] The bonding pad is formed by forming a conductive material layerwhich completely covers the grooves on the insulating layer, followed bypolishing the conductive material layer by the CMP. The passivationlayer is etched by the RIE and the etching stopper layer is etched bythe RIE or CDE.

[0080] As the grooves are filled with the conductive material, thebonding pad and the uppermost wiring layer are formed at the same time.

[0081] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outin the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0082] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate presently preferredembodiments of the invention, and together with the general descriptiongiven above and the detailed description of the preferred embodimentsgiven below, servo to explain the principles of the invention.

[0083]FIG. 1 is a plan view showing a conventional semiconductor device;

[0084]FIG. 2 is a cross sectional view taken along the line II-IIindicated in FIG. 1;

[0085]FIG. 3 is a plan view showing a conventional semiconductor device;

[0086]FIG. 4 is a cross sectional view taken along the line IV-IVindicated in FIG. 3;

[0087]FIG. 5 is a diagram showing a dishing phenomenon which may occurin conventional damascening process;

[0088]FIG. 6 is a plan view showing a conventional semiconductor device;

[0089]FIG. 7 is a cross sectional view taken along the line VII-VIIindicated in FIG. 6;

[0090]FIG. 8 is a cross sectional view of a device, which illustrate astep of a conventional manufacturing method;

[0091]FIG. 9 is a cross sectional view of a device, which illustrateanother step of the conventional manufacturing method;

[0092]FIG. 10 is a cross sectional view of a device, which illustratestill another step of the conventional manufacturing method;

[0093]FIG. 11 is a cross sectional view of a device, which illustratestill another step of the conventional manufacturing method;

[0094]FIG. 12 is a cross sectional view of a device, which illustratestill another step of the conventional manufacturing method;

[0095]FIG. 13 is a cross sectional view of a device, which illustratestill another step of the conventional manufacturing method;

[0096]FIG. 14 is a cross sectional view of a device, which illustratestill another step of the conventional manufacturing method;

[0097]FIG. 15 is a cross sectional view of a device, which illustratestill another step of the conventional manufacturing method;

[0098]FIG. 16 is a plan view of a device, which illustrates a step ofthe conventional manufacturing method;

[0099]FIG. 17 is a cross sectional view taken along the line XVII-XVIIindicated in FIG. 16;

[0100]FIG. 18 is a plan view of a device, which illustrates a step ofthe conventional manufacturing method;

[0101]FIG. 19 is a cross sectional view taken along the line XIX-XIXindicated in FIG. 18;

[0102]FIG. 20 is a cross sectional view of a device, which illustrates astep of the conventional manufacturing method;

[0103]FIG. 21 is a plan view of a device, which illustrates a step ofthe conventional manufacturing method;

[0104]FIG. 22 is a cross sectional view taken along the line XXII-XXIIindicated in FIG. 21;

[0105]FIG. 23 is a plan view which illustrates a state in which wirebonding is carried out on the device shown in FIG. 6;

[0106]FIG. 24 is a cross sectional view taken along the line XXIV-XXIVindicated in FIG. 23;

[0107]FIG. 25 is a plan view of a semiconductor device according to anembodiment of the present invention;

[0108]FIG. 26 is a cross sectional view taken along the line XXVI-XXVIindicated in FIG. 25;

[0109]FIG. 27 is a cross sectional view of a device, which illustrates astep of a manufacturing method according to an embodiment of the presentinvention;

[0110]FIG. 28 is a cross sectional view of a device, which illustratesanother step of a manufacturing method according to the embodiment ofthe present invention;

[0111]FIG. 29 is a cross sectional view of a device, which illustratesstill another step of a manufacturing method according to the embodimentof the present invention;

[0112]FIG. 30 is a cross sectional view of a device, which illustratesstill another step of a manufacturing method according to the embodimentof the present invention;

[0113]FIG. 31 is a cross sectional view of a device, which illustratesstill another step of a manufacturing method according to the embodimentof the present invention;

[0114]FIG. 32 is a cross sectional view of a device, which illustratesstill another step of a manufacturing method according to the embodimentof the present invention;

[0115]FIG. 33 is a cross sectional view of a device, which illustratesstill another step of a manufacturing method according to the embodimentof the present invention;

[0116]FIG. 34 is a cross sectional view of a device, which illustratesstill another step of a manufacturing method according to the embodimentof the present invention;

[0117]FIG. 35 is a plan view of a device, which illustrates a step of amanufacturing method according to an embodiment of the presentinvention;

[0118]FIG. 36 is a cross sectional view taken along the line XXXVI-XXXVIindicated in FIG. 35;

[0119]FIG. 37 is a plan view of a device, which illustrates a step of amanufacturing method according to an embodiment of the presentinvention;

[0120]FIG. 38 is a cross sectional view taken along the lineXXXVIII-XXXVIII indicated in FIG. 37;

[0121]FIG. 39 is a cross sectional view of a device, which illustrates astep of a manufacturing method according to an embodiment of the presentinvention;

[0122]FIG. 40 is a plan view of a device, which illustrates a step of amanufacturing method according to the embodiment of the presentinvention;

[0123]FIG. 41 is a cross sectional view taken along the line XLI-XLIindicated in FIG. 40;

[0124]FIG. 42 is a plan view of a device, which illustrates a step of amanufacturing method according to an embodiment of the presentinvention;

[0125]FIG. 43 is a cross sectional view taken along the line XLIII-XLIIIindicated in FIG. 42;

[0126]FIG. 44 is a plan view which illustrates a state in which wirebonding is carried out on the device shown in FIG. 25; and

[0127]FIG. 45 is a cross sectional view taken along the line XLV-XLVindicated in FIG. 44.

DETAILED DESCRIPTION OF THE INVENTION

[0128] Semiconductor devices of the present invention and methods ofmanufacturing the same will now be described in detail with reference toembodiments thereof shown in accompanying drawings.

[0129]FIGS. 25 and 26 show a semiconductor device formed by the dualdamascening process according to an embodiment of the present invention.FIG. 26 is a cross sectional view taken along the line XXVI-XXVIindicated in FIG. 25.

[0130] As can be seen in the figure, a field oxide layer 12 is formed ona semiconductor substrate 11. In an element region surrounded by thefield oxide layer 12, a MOS transistor having a source-drain region 13and a gate electrode 14, is formed.

[0131] On the semiconductor substrate 11, insulating layers 15 and 24are formed so as to completely cover the MOS transistor. A contact hole16 a is made in the insulating layers 15 and 24 from its surface to bethrough to the source-drain region 13.

[0132] The insulating layer 25 is formed on the insulating layer 24. Inthe insulating layer 25, a plurality of grooves 16 b used for forming afirst-level wiring layer, are formed. Bottom sections of the pluralityof grooves 16 b are made through to the contact hole 16 a.

[0133] A barrier metal 17 a is formed on an inner surface of each of thecontact hole 16 a and the grooves 16. Further, on each of the barriermetals 17 a, a metal (or metal alloy) portion 17 b is formed so as tocompletely fill each of the contact hole 16 a and the grooves 16 b. Theplurality of wirings which make the first level wiring layer, consist ofthe barrier metals 17 a and the metal portions 17 b.

[0134] A contact plug used for connecting the first level wiring layerand the source-drain region 13 of the MOS transistor to each other, alsoconsists of the barrier metal 17 a and the metal portion 17 b. Thesurface of the insulating layer 25 meets with that of the first-levelwiring layer, and the surface is made flat.

[0135] On the insulating layer 25 and the first level wiring layer, theinsulating layer (interlayer dielectric) 18 and the insulating layer 26are formed. A contact hole 19 a is formed in the insulating layers 18and 26 from its surface to be through to the first-level wiring layer.

[0136] An insulating layer 27 is formed on the insulating film 26. Aplurality of grooves 19 b used for forming the second-level wiringlayer, are formed in the insulating layer 27. Bottom sections of theplurality of grooves 19 b are made through to the contact hole 19 a.

[0137] A barrier metal 20 a is formed on an inner surface of each of thecontact hole 19 a and the grooves 19 b. Further, on each of the barriermetals 20 a, a metal (or metal alloy) portion 20 b is formed so as tocompletely fill each of the contact hole 19 a and the grooves 19 b. Theplurality of wirings which make the second level wiring layer, consistof the barrier metals 20 a and the metal portions 20 b.

[0138] A contact plug used for connecting the first-level wiring layerand the second-level wiring layer to each other, also consists of thebarrier metal 20 a and the metal portion 20 b. The surface of theinsulating layer 27 meets with that of the second-level wiring layer,and the surface is made flat.

[0139] In the case where the second-level wiring layer is located as theuppermost layer, a part of the second-level wiring layer constitutes abonding pad 21. The bonding pad 21 is made of a metal (or metal alloy),as in the case of the second-level wiring layer. However, in order toprevent the dishing which may occur during the CMP, the bonding pad 21is formed to have, for example, a lattice-like shape.

[0140] Further, an etching stopper layer 29 is formed on the insulatinglayer 27 and the second-level wiring layer, and a passivation layer(passivation dielectric) 22 is formed on the etching stopper layer 29.

[0141] The etching stopper layer 29 is made of a material which can beetched selectively with respect to the material used for the insulatinglayer 27 and the passivation layer 22. For example, in the case wherethe insulating layer 27 and the passivation layer 22 are made of siliconoxide, the etching stopper layer 29 is made of silicon nitride. Theetching stopper layer 29 is formed to have a thickness of about 50 nm.

[0142] An opening 23 is made in the passivation layer 22 and the etchingstopper layer 29 so as to expose the bonding pad 21.

[0143] In the semiconductor device manufactured by the dual damasceningprocess, the bonding pad 21 is formed to have a lattice-like shape.Therefore, even in the case where the bonding pad 21 is formed by use ofthe CMP technique, the necessary portion thereof is not excessivelyetched, thereby effectively preventing the dishing.

[0144] Further, the bonding pad 21 having a lattice shape is completelyfilled with the insulating layer 27. With this structure, the bondingpad 21 is not squashed or deformed when the wire is bonded thereto bycompression by wire bonding. Therefore, the occurrence of bonding errorsis suppressed, thus contributing the improvement of the reliability andthe yield of the product.

[0145] Furthermore, directly underneath the passivation layer 22, theetching stopper layer 29 is located, which is made of a material whichcan be etched selectively with respect to the material used for formingthe passivation layer 22 and the insulating layer 27. With thisstructure, the portions of the insulating layer 27, which are situatedin the lattice-like formations of the bonding pad 21, are not etchedwhen the opening 23 is made in the passivation layer 22.

[0146] Next, the method of manufacturing a semiconductor device shown inFIGS. 25 and 26 will be described.

[0147] First, as can be seen in FIG. 27, with the LOCOS method, a fieldoxide layer 12 is formed on a silicon substrate 11. After that, in anelement region surrounded by the field oxide layer 12, a MOS transistorhaving a source-drain region 13 and a gate electrode 14 is formed.

[0148] Further, as an alternative, an insulating film (borophosphosilicate glass (BPSG) or the like) 15 having a thickness of about 1 μm,which completely covers the MOS transistor, is formed on the siliconsubstrate 11. The surface of the insulating layer 15 is made flat by theCMP.

[0149] Next, as can be seen in FIG. 28, an etching stopper layer 24 andan insulating layer 25 are formed continuously on the insulating film 15with the CVD method, for example. The insulating layer 25 is made of,for example, silicon oxide. In the case where the insulating layer 25 ismade of silicon oxide, the etching stopper layer 24 is made of amaterial having a high etching selectivity against silicon oxide inreactive ion etching (RIE), that is, for example, silicon nitride.

[0150] The thickness of the etching stopper layer 24 is set to about 50nm, and the thickness of the insulating film 25 is set to the same asthat of the wirings which constitute the first-level wiring layer, thatis, for example, about 0.6 μm.

[0151] Next, as can be seen in FIG. 29, a plurality of grooves 16 b areformed in the insulating layer 25. The plurality of grooves 16 b areformed by a photo engraving process, more specifically, the applicationof a resist on the insulating layer 25, the patterning of the resist,the etching of the insulating layer 25 by RIE using the resist as amask, and the removal of the resist. The etching stopper layer 24 servesas an etching stopper for the RIE.

[0152] It should be noted that the pattern of the plurality of grooves16 b is made to match with the pattern of the wirings which constitutethe first-level wiring layer.

[0153] Next, as can be seen in FIG. 30, a contact hole 16 a is made inthe insulating layers 15 and 24. The contact hole 16 a is made also bythe photo engraving process as in the formation of the plurality ofgrooves 16 b. More specifically, the contact hole 16 a is made byapplying a resist on the insulating layer 25 and in the grooves 16 b,patterning the resist, etching the insulating layers 15 and 24 by theRIE using the resist as a mask, and removing the resist.

[0154] Then, as can be seen in FIG. 31, a barrier metal 17 a is formedon the insulating layer 25, on an inner surface of the contact hole 16 aand the inner surfaces of the grooves 16 b, by the CVD method or PVDmethod. The barrier metal 17 a is made of, for example, a lamination oftitanium and titanium nitride, or silicon titanium nitride, or the like.

[0155] Next, as can be seen in FIG. 32, a metal (or metal alloy) portion17′ which completely covers the contact hole 16 a and the grooves 16 b,is formed on the barrier metal 17 a by the CVD or PVD method. The metalportion 17′ is made of, for example, aluminum, copper or an alloy ofthese metals.

[0156] As the PVD method which is used to form the metal portion 17′,the high temperature PVD method or a PVD method including such atemperature process that can completely fill the contact holes 16 a andthe grooves 16 b, is used.

[0157] Next, as can be seen in FIG. 33, the sections of the barriermetal 17 a and the metal portion 17 b, which are situated outside thecontact holes 16 a and the grooves 16 b, are etched by the CMP method,so that the barrier metal 17 a and the metal portion 17 b remain only inthe contact holes 16 a and the grooves 16 b.

[0158] In this manner, the first-level wiring layer is formed, and atthe same time, a contact plug which serves to electrically connect thefirst-level wiring layer and the diffusion layer (source-drain region)of the substrate to each other, is formed.

[0159] Next, as can be seen in FIG. 34, an insulating layer (forexample, silicon oxide) 18 having a thickness of about 1 μm, is formedon the insulating layer 25 and the first-level wiring layer by the CVDmethod. Further, an etching stopper layer 26 and an insulating layer 27are formed to be continuous on the insulating film 18 with the CVDmethod, for example. The insulating layer 27 is made of, for example,silicon oxide. In the case where the insulating layer 27 is made ofsilicon oxide, the etching stopper layer 26 is made of a material havinga high etching selectivity against silicon oxide in reactive ion etching(RIE), that is, for example, silicon nitride.

[0160] The thickness of the etching stopper layer 26 is set to about 50nm, and the thickness of the insulating film 27 is set to the same asthat of the wirings which constitute the second-level wiring layer.

[0161] Next, as can be seen in FIGS. 35 and 36, a plurality of grooves19 b and 19 b′ are formed in the insulating layer 25. The plurality ofgrooves 19 b and 19 b′ are formed by a photo engraving process, morespecifically, the application of a resist on the insulating layer 27,the patterning of the resist, the etching of the insulating layer 27 byRIE using the resist as a mask, and the removal of the resist. Theetching stopper layer 26 serves as an etching stopper for the RIE.

[0162] It should be noted that the pattern of the plurality of grooves19 b and 19 b′ is made to match with the pattern of the wirings whichconstitute the second-level wiring layer. The pattern of the grooves 19b′ is the same as that of the bonding pad (lattice-like shape) (in thecase where the second-level wiring layer is the uppermost layer).

[0163] Next, as can be seen in FIGS. 37 and 38, a contact hole 19 a ismade in the insulating layers 18 and 26. The contact hole 16 a is madealso by the photo engraving process as in the formation of the pluralityof grooves 19 b and 19 b′. More specifically, the contact hole 19 a ismade by applying a resist on the insulating layer 27 and in the grooves19 b and 19 b′, patterning the resist, etching the insulating layers 18and 26 by the RIE using the resist as a mask, and removing the resist.

[0164] After that, a barrier metal 20 a is formed on the insulatinglayer 27, on an inner surface of the contact hole 19 a and the innersurfaces of the grooves 19 b and 19 b′, by the CVD method or PVD method.The barrier metal 20 a is made of, for example, a lamination of titaniumand titanium nitride, or silicon titanium nitride, or the like.

[0165] Next, metal (or metal alloy) portions 20 b and 21 whichcompletely cover the contact hole 19 a and the grooves 19 b and 19 b′,are formed on the barrier metal 20 a by the CVD or PVD method. The metalportions 20 b and 21 are made of, for example, aluminum, copper or analloy of these metals.

[0166] As the PVD method which is used to form the metal portions 20 band 21, the high temperature PVD method or a PVD method including such atemperature process that can completely fill the contact hole 16 a andthe grooves 19 b and 19 b′, is used.

[0167] Next, the sections of the barrier metal 20 a and the metalportions 20 b and 21, which are situated outside the contact hole 19 aand the grooves 19 b and 19 b′, are etched by the CMP method, so thatthe barrier metal 20 a and the metal portions 20 b and 21 remain only inthe contact hole 19 a and the grooves 19 b and 19 b′.

[0168] In this manner, the second-level wiring layer and the bonding padhaving a lattice-like shape are formed, and at the same time, a contactplug which serves to electrically connect the first-level wiring layerand the second-level wiring layer to each other, is formed.

[0169] Next, as can be seen in FIG. 39, an etching stopper layer 29 anda passivation layer 22 are formed to be continuous, on the insulatinglayer 27, the second-level wiring layer and the bonding pad, by, forexample, the CVD method.

[0170] The passivation layer 22 is made of, for example, silicon oxide.In the case where the passivation layer 22 is made of silicon oxide, theetching stopper layer 29 is made of a material having a high etchingselectivity against silicon oxide in reactive ion etching (RIE), thatis, for example, silicon nitride. The thickness of the etching stopperlayer 29 is set to about 50 nm.

[0171] Next, as can be seen in FIGS. 40 and 41, an opening 23 is formedin the passivation layer 22. The opening 23 is situated so as to thelattice-shaped bonding pad 21, and is formed by a photo engravingprocess, more specifically, the application of a resist on theinsulating layer 22, the patterning of the resist, the etching of theinsulating layer 22 by RIE using the resist as a mask, and the removalof the resist.

[0172] In the RIE operation for making the opening 23, the insulatinglayer 27 is not etched in the presence of the insulating layer 27.

[0173] Then, as can be seen in FIGS. 42 and 43, only the etching stopperlayer 29 remaining in the bottom of the opening 23 of the passivationlayer 22 is removed. The removal of the etching stopper layer 29 can beachieved by anisotropic etching such as RIE, or isotropic etching suchas chemical dry etching (CDE).

[0174] As described above, the semiconductor device shown in FIGS. 25and 26 is completed.

[0175] The feature of the above-described method is that the etchingstopper layer 29 is provided directly underneath the passivation layer22. With this structure, in the RIE operation carried out to made theopening 23 in the bonding pad 21, the sections of the insulating layer27 formed in the lattice-like pattern of the bonding pad 21 are notetched.

[0176] More specifically, as can be seen in FIGS. 44 and 45, therecessed pattern of the lattice-shaped bonding pad 21 is filled with theinsulating layer 27. With this structure, even if the wire bonding iscarried out, the wire 28 does not squash or deform the lattice-shapedbonding pad 21.

[0177] Therefore, the bonding error can be avoided, thereby making itpossible to improve the reliability and yield of the product.

[0178] As described above, with the semiconductor device and the methodof manufacturing such a device, according to the present invention, thefollowing effect can be obtained.

[0179] That is, directly underneath the passivation layer, an etchingstopper layer is provided. Therefore, in the RIE operation for making anopening to expose the bonding pad, the portions of the insulating layer,which are situated at the recessed portions of the lattice shape, arenot etched. Consequently, each section between adjacent recessedportions is filled with the insulation layer. With this structure, if awire bonding is carried out, the wire cannot squash or deform thebonding pad having a lattice-like shape. Thus, the bonding error can beprevented, thereby making it possible to improve the reliability andyield of the product.

[0180] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

1. A semiconductor device having a bonding pad constituted by aconductive member filled in grooves made in an insulating layer having aflat surface, said semiconductor device comprising: an etching stopperlayer formed on said insulating layer and having an opening to exposesaid bonding pad; and a passivation layer formed on said etching stopperlayer and having an opening to expose said bonding pad.
 2. Asemiconductor device according to claim 1, wherein said grooves in saidinsulating layer are arranged in a lattice manner, and said bonding padhas a lattice-like shape.
 3. A semiconductor device according to claim1, wherein said insulating layer and said passivation layer are made ofsilicon oxide, and said etching stopper layer is made of siliconnitride.
 4. A semiconductor device according to claim 1, furthercomprising wirings filled in said grooves of said insulating layer.
 5. Asemiconductor device according to claim 1, wherein said bonding pad andsaid wirings are constituted by a first metal layer and a second metallayer made of a metal different from that of the first metal layer,respectively.
 6. A semiconductor device according to claim 1, whereinthe first metal layer is made of titanium and titanium nitride, orsilicon titanium nitride, and the second metal layer is made ofaluminum, copper or an alloy thereof.
 7. A semiconductor deviceaccording to claim 1, further comprising a wire connected to saidbonding pad.
 8. A method of manufacturing a semiconductor device, inwhich a bonding pad is formed by making grooves in an insulating layerhaving a flat surface and filling the grooves with a conductivematerial, the method including the stops of: forming said bonding pad byfilling said grooves of said insulating layer with said conductivematerial; forming an etching stopper layer on said insulating layer andthe bonding pad, said etching stopper layer being made of a materialwhich can be etched selectively with respect to at least a materialwhich is used to form said insulating layer; forming a passivation layeron said etching stopper layer, said passivation layer being made of amaterial which can be etched selectively with respect to at least thematerial used to form said etching stopper layer; removing only aportion of said passivation layer, which is situated above the bondingpad; and removing only a portion of said etching stopper layer, which issituated above the bonding pad.
 9. A method of manufacturing asemiconductor device, according to claim 8, wherein said bonding pad isformed by a step of forming a conductive material on said insulatinglayer so as to completely fill said grooves therewith, and a step ofpolishing said conductive material by a CMP technique.
 10. A method ofmanufacturing a semiconductor device, according to claim 8, wherein saidpassivation layer is etched by an RIE technique and said etching stopperlayer is etched by an RIE or CDE technique.
 11. A method ofmanufacturing a semiconductor device, according to claim 8, wherein saidbonding pad and said wirings are formed at the same time by filling saidgrooves with the conductive material.
 12. A method of manufacturing asemiconductor device, according to claim 8, wherein said bonding pad andsaid wirings are formed by a dual damascening process or damasceningprocess.
 13. A method of manufacturing a semiconductor device, accordingto claim 8, wherein a wire is connected to said bonding pad in a wirebonding process.